Jan Alexander Steffens authored Jul 11, 2019 and Arun Raghavan committed Jul 25, 2019

 - Rename "pulsedspdir" to the same "padsplibdir" that Autotools uses.

 - Add a new option "pulsedsp-location" that is only used for padsp.in,
   just like Autotools' --with-pulsedsp-location.

 - Use 'set' instead of 'set_quoted' to avoid PULSEDSP_LOCATION getting
   quoted twice.